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Issue 03/2017

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bioplasticsMAGAZINE_1703

Opinion Could the wax

Opinion Could the wax moth solve the problem of PE plastic waste? Food for thought I’m a beekeeper, so I know only too well what havoc the wax moth (or better the larvae of the greater wax moth Galleria mellonella) can wreak on the wax combs in my bee hives. Secondly, I also know that the wax moth is mainly interested in wax combs used by the bees to breed their offspring. Obviously, they are more interested in the proteins from the cocoons that remain behind in the chambers after the bees have hatched. In fact, the wax moths don’t touch honeycombs, which are only used by the bees to store honey. They only attack the brood combs. And thirdly, I’m an engineer by education, and therefore have a scientific background. Hence, I’m always reluctant to believe in miraculous findings that create huge hype in the media - especially when they are hailed as being THE solution for the world’s plastic waste problem. That said, I must admit that I really was excited about the recent news – my interest piqued by various catchy headlines, such as “A Very Hungry Caterpillar Eats Plastic Bags” [1, 2]. The wax moth and polyethylene It all started when Federica Bertocchini, a scientist and herself a beekeeper, found to her astonishment after cleaning up and disposing of the mess wax worms had created in her beehives, that the worms appeared to be eating the PE-bags she had used to dispose of them in [2]. Together with Paolo Bombelli and Christopher J. Howe at the University of Cambridge, she decided to investigate further [3]. They embarked on some serious research: performing FTIR analyses and even mashing wax worms up (a kind of revenge?) to smear the wax worm paste on Polyethylene to see what would happen. And indeed, they discovered that the substance that the caterpillars left behind included polyethylene glycol. A sign of biodegradation? Professor Ramani Narayan from Michigan State University, a respected expert in the field of biodegradation of plastics says, that “the paper [3] provides no evidence that the PE carbons is being completely utilized by the wax moths and removed from the environmental compartment -- as measured by the evolved CO 2 from biological metabolism based on accepted International standards for measuring and reporting biodegradability” [4]. A solution to tackle the problem of plastic litter? Ramani Narayan is not convinced. “The study of the interaction of PE plastic with wax moths may be useful and provide for interesting biology,” he says. “However, to widely extrapolate the fragmentation of the PE film as a biodegradation concept that is a solution for plastic waste management is very misleading and troublesome. The formation of holes in a plastic bag due to mechanical action (chewing of the film) and resultant loss of mass suggests fragmentation and release of the small fragments into the environment. This has the potential to cause harm to the environment and human health” [4]. And he goes on: “Biodegradation is not a magical solution to plastics waste management. To the contrary, release of small fragments (microplastics) into the terrestrial and ocean environment has been shown to cause harm to the environment and to human health. Many papers in the literature document that such fragments pick up toxins from the environment like a sponge and become a vehicle to transport toxins up the food chain. Complete biodegradation of single use disposable plastics along with food and other biowastes in managed, closed loop disposal systems like composting and anaerobic digestion is environmentally responsible. This helps divert food and other biowastes from landfills and oceans. As a matter of fact, the State of California prohibits the unqualified use of the term biodegradable and only certified fully biodegradable-compostable plastics going into industrial composting systems are allowed. The U.S. Federal Trade Commission (U.S. FTC) has similar guidance on the use of terms like biodegradable and compostable.” Another interesting thought was published by The Guardian [5]: The wax moth is a pest (remember, I’m a beekeeper myself – and I can confirm). Wax moths are socalled because they love to eat the wax from which bees make their honeycombs – and so they can really devastate bee colonies. Wax moths in their different species are thought to cause more than (USD 5.2 million) worth of damage annually in the United States alone. With bee populations already under severe stress from many different reasons, we probably should not start breeding one of their common airborne enemies in huge numbers. Bees play a crucial role in maintaining healthy and thriving plant communities. Interfering in nature is something we’ve done before - and usually with less-thanpropitious results. With bee numbers already on the decline, breeding wax moths just might create more problems than it solves. Plastic pollution is our mess, a result of our behaviour, and we need to take responsibility for fixing the 40 bioplastics MAGAZINE [03/17] Vol. 12

Automotive Opinion By: Michael Thielen problem. Pinning our hopes on the appetite of the wax moth larva would somehow not seem the best strategy for doing so. And the science? Back to Federica Bertocchini and her fellow researchers: Ramani Narayan points out that the claim of fast biodegradation to ethylene glycol based on a 3300 cm -1 band in the FTIR is tenuous at best - anyone with knowledge of FTIR would say that the observed peak simply represents a –O-H stretching vibration which could be due to physically adsorbed water. Proteins and carbohydrates of the wax worm and their extracts would contribute to hydroxyl and carbonyl signatures. It is not clear as to how this was addressed or even if it was addressed. The authors report a carbonyl; C=O peak in the FTIR, which is not consistent with proposed ethylene glycol formation. Again carbonyl peaks can arise from residual proteins of the wax worm [4]. And finally… it’s not as new as we may think. In 2014, Chinese scientists published findings on “Polyethylene biodegradation by bacterial strains from the guts of plastic eating waxworms” [6, 7]. Back then, however, the news escaped the lurid, sensationalist coverage that created the current hype without seriously questioning the facts. (Photo: Federica Bertocchini, Paolo Bombelli, and Chris Howe) References [1] Bromwich, J.E., A Very Hungry Caterpillar Eats Plastic Bags, The New York Times, https://www.nytimes.com/2017/04/27/science/plasticeating-caterpillar.html?_r=0 [2] Yong, E.: The very hungry plastic eating caterpillar, The Atlantic, https:// www.theatlantic.com/science/archive/2017/04/the-very-hungry-plasticeating-caterpillar/524097/ [3] Bombelli, P.; Howe, C.J.; Bertocchini, F.: Polyethylene bio-degradation by caterpillars of the wax moth Galleria mellonella, Current Biology 27, R1–R3, April 3, 2017 [4] Narayan, R.: Comments on the publication as cited in [3], www.bioplasticsmagazine.de/201703 [5] Yong, E.: The Very Hungry Plastic-Eating Caterpillar, The Guardian, https://www.theguardian.com/commentisfree/2017/apr/25/plasticeating-bugs-wax-moth-caterpillars-bee [6] N.N.: Gut bacteria from a worm can degrade plastic; https://www. acs.org/content/acs/en/pressroom/presspacs/2014/acs-presspacdecember-3-2014/gut-bacteria-from-a-worm-can-degrade-plastic. html [7] Yang, J. et.al.: Evidence of Polyethylene Biodegradation by Bacterial Strains from the Guts of Plastic-Eating Waxworms, http://pubs.acs.org/ doi/abs/10.1021/es504038a My bees, healthy and busy Wax combs destroyed by Galleria mellonella © Maja Dumat bioplastics MAGAZINE [03/17] Vol. 12 41

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